Gunnera tinctoria is currently considered invasive on the west coast of Ireland, although it is also found on the east coast to date it is not
considered invasive. It is considered to be having a significant impact on Achill Island, County Mayo, where is has spread throughout.

It is thought it was originally bought over as an ornamental plant; first records of it are as far back as 1939 (Praeger). Its native
range is mainly from southern Chile, where climatic conditions are similar to those found on the west coast, high annual rainfall and
temperatures rarely falling below 0º C.

In Ireland it is now found on coastal cliffs, waterways, roadsides, wet meadows and derelict gardens and fields.
It propagates both by seed and by vegetative means. In early spring its leaves begin to grow and in a couple of weeks can reach over
2 meters in height. Its large leaves (up to 2m wide) and fast growth shade all plants growing below. In the winter the leaves die back
leaving the exposed rhizomes.

IDENTIFICATION

Whilst Gunnera is difficult to confuse with any other species in the Irish flora, or in an Irish garden, the
differences between G.tinctoria and G.manicata are less obvious and in view of the fact that
the former is highly invasive and the latter apparently not (as yet), it is important to distinguish between
them.

The most reliable method is the apperance of the inflorescence: on the right is an image of the two inflorescences: G.tinctoria on the left, and G.manicata
on the right.

CONTROL

Control has been focused on the use of herbicides. Currently trials are being carried out in Dooega, Achill Island using RoundUp (glyphosate) and Garlon (triclopyr).

There has been initial success, although it is expected that further applications will be necessary due to the large rhizome of fully established plants.

In New Zealand, where it is also invasive, there have been experiments with several herbicides for a number of years and aerial spraying over large areas has been conducted.
The New Zealand Department of Conservation (DoC) have reported their suggestions on the control of G. tinctoria. (Williams et al. 2005).

Alongside the experiments a mapping project of Achill Island is being conducted. The mapping will provide a baseline for future projects to monitor its spread and the success of control.
It will provide an insight into the habitats at risk of invasion, its means of spread and where prevention could be introduced as a means of control. Currently as part of this project an information leaflet for landowners is being produced.

DISTRIBUTION
Reynolds (2002):
Fairly common escape from cultivation, mainly in W and SW; naturalized extensively in parts of W Mayo (Achill Island and Curraun) and W Galway (Connemara); boggy ground, damp pastures, ditches, roadsides, by streams etc.; freely seeding, and also spreading from discarded plants or from where originally planted; considered an invasive species, the effect of G. tinctoria on semi-natural grassland habitats has been studied (Hickey & Osborne 1998).

* Naturalized and plentiful by mid-1930s on rough hillsides on S side of Killary Harbour below Leenane in W Galway; also N side of Killary Harbour, and on shore and in gullies on S side of Curraun Achill in W Mayo (as G. manicata in Praeger 1939; see FCB 1983).